I've used the data logger 3 times (Evo IX). The first time I used it I hit OK to get it started, but I didn't allow it time to connect so by the time it started keeping a log I was already at freeway speed.
After maybe 20 seconds I hit OK again to stop the logging, but when I got home the log was 9 minutes long.
The second time I went out I decided not to stop the logging to see what the max length is (9 minutes again?). But when I got home the log was only 5 seconds long. I figured that the AP must've lost its connection for a moment.
Third time I logged for half a minute, then hit OK to stop it, went to a gas station, shut off motor. When I left I tried to log again to see what would happen. It said it wasn't logging, which I took to mean it wouldn't let me because it wanted to preserve the already logged data. But when I got home there was no file. Hopefully, next time it'll have a log.
Btw, I opened my log files in Works Spreadsheet. Worked just fine for viewing the csv files.